net: phylib: add link_change_notify callback to phy device

Add a notify callback to inform phy drivers when the core is about to
do its link adjustment. No change for drivers that do not implement
this callback.

Signed-off-by: Daniel Mack <zonque@gmail.com>
Signed-off-by: David S. Miller <davem@davemloft.net>
diff --git a/include/linux/phy.h b/include/linux/phy.h
index 864ddaf..6804144 100644
--- a/include/linux/phy.h
+++ b/include/linux/phy.h
@@ -536,6 +536,15 @@
 	/* See set_wol, but for checking whether Wake on LAN is enabled. */
 	void (*get_wol)(struct phy_device *dev, struct ethtool_wolinfo *wol);
 
+	/*
+	 * Called to inform a PHY device driver when the core is about to
+	 * change the link state. This callback is supposed to be used as
+	 * fixup hook for drivers that need to take action when the link
+	 * state changes. Drivers are by no means allowed to mess with the
+	 * PHY device structure in their implementations.
+	 */
+	void (*link_change_notify)(struct phy_device *dev);
+
 	struct device_driver driver;
 };
 #define to_phy_driver(d) container_of(d, struct phy_driver, driver)